JP2985533B2 - High transmission efficiency photocoupler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facing type photocoupler in which a light emitting element and a light receiving element face each other, and more particularly to a photocoupler having a high transmission efficiency relating to an internal structure of an optical coupling element (photocoupler).

[0002]

2. Description of the Related Art In recent years, various devices have been reduced in size and power consumption has been reduced, and photocouplers have also been required to be reduced in size and have higher transmission efficiency. As a general usage of the photocoupler, the photocoupler is used for signal transmission between two substrates having different reference potentials. Therefore, the photocoupler must transmit signals between the two substrates while maintaining electrical insulation between the two substrates.

For the purpose of improving the dielectric strength, a double-mold photocoupler as shown in FIG. 6 (a cross-sectional structure diagram of a conventional example) has been developed. This is the light emitting element 41 and the light receiving element
With the 42 facing each other, the primary mode and the secondary mode are further performed on it to increase the distance between the different substance interfaces between the input (light emitting element 41 side) and the output (light receiving element 42 side). In addition, the withstand voltage is improved. Also, this double mold coupler has
A structure in which the light-emitting element 41 is covered with a light-transmitting protective agent (generally, a silicone resin 47) for the purpose of protecting the light-emitting element 41 from thermal and mechanical stress applied after the assembly process, that is, light-transmitting property. It has a "single-step coating structure" made of a silicone resin 47 as a protective agent.

The above-mentioned conventional photocoupler will be described in further detail with reference to FIG. 6. This structure comprises a pair of a light emitting element 41 and a light receiving element 42, and a light emitting side lead frame 45 and a light receiving side lid. -Pellet mounted on the do frame 46 and wire-bonded. 43 is a bonding wire (Au line on the light emitting element side) and 44 is a bonding wire (Au line on the light receiving element side). The light emitting element 41 is made of a light transmitting protective agent (silicon resin 4) to avoid thermal and mechanical stress.
7) is coated (one-step coating), and the whole is covered with a primary mold resin (translucent resin) 48, and the outside is covered with a secondary mold resin (light-shielding resin) 49. It is of the structure that was built.

Next, the operation of the conventional photocoupler will be described. First, the light emitting element 41 is turned on by an electric signal input from the input side lead of the light emitting side lead frame 45, and then this optical signal is transmitted to the silicone resin 47 and the primary mold resin (light transmitting resin). The light reaches the light-receiving element 42 via the conductive resin 48, where it is converted into an electric signal again and output from the output-side lead of the light-receiving-side lead frame 46.

[0006] Such an optical coupling element (photocoupler)
As described above, the purpose of the present invention is to provide electrical insulation between input and output by transmitting a signal by light, and the withstand voltage is generally 2.5 to 5 kV.

[0007]

As described above, in recent years, there has been a demand for downsizing and high transmission efficiency of photocouplers. That is, it has been required to reduce the size and output a large signal with a small amount of input signal (higher transmission efficiency).

In order to reduce the size, it is considered (1) to reduce the distance between the light emitting element and the light receiving element, and to increase the transmission efficiency, it is the same as (2) to reduce the size. To reduce the distance between the light emitting element and the light receiving element, (3) to increase the efficiency of the light emitting element and the light receiving element, and (4) to increase the transmittance of the primary mold resin (translucent resin). ,
And various improvement proposals have been made conventionally.

However, among the above-mentioned conventional improvement methods,
(1) and (2) “Reducing the distance between the light emitting element and the light receiving element” has a drawback that the dielectric strength is reduced. Further, the above (3) “To improve the efficiency of the light-emitting element and the light-receiving element” has problems such as adoption of a new structure and upsizing of the chip, resulting in an increase in cost.

Further, with respect to the above (4) "To increase the transmittance of the primary mold resin (translucent resin)", the releasability, the moldability, and the reliability in the resin mold. Since it is necessary to mix various additives such as fillers, mold release agents, and curing accelerators into the translucent primary mold resin material in order to improve the properties and the like, the light with respect to light having a wavelength of about 700 to 1000 nm is required. The transmittance can be increased only up to about 20% / mm at most, and it is difficult to improve the light transmittance of the photocoupler by (4).

The conventional dual mode shown in FIG.
Photocouplers (photocouplers having a one-step coating structure of a light-transmitting protective agent) have the following problems and disadvantages. In the one-step application of such a light-transmitting protective agent, the function of condensing the light emitted from the light-emitting element is poor. In an example in which a phototransistor is used for a light-receiving element, the transfer efficiency (output current / input current) is: It was common that only about 300% could be issued.

On the other hand, in the market, there is a demand for a photocoupler of 400% or more. To meet this demand, a light receiving element is conventionally amplified by a Darlington type phototransistor. However, this has the disadvantage that the response speed is slow and some requests cannot be answered.

An object of the present invention is to provide a photocoupler which solves the above-mentioned problems and disadvantages. More specifically, the present invention provides a photocoupler which can easily and easily maintain the actual withstand voltage between the input and output of the photocoupler. Another object of the present invention is to provide a double-molded photocoupler with high transmission efficiency that can increase transmission efficiency at low cost.

[0014]

The high transmission efficiency photocoupler of the present invention is characterized in that: (1) First, two or more light-transmitting coating resins for protecting the light-emitting element are overlapped. 2) Second, light-transmitting polyimide resin
Characterized by covering the fat, (3) Third, be combined above (1) and (2), i.e.,
The light emitting device is characterized in that two or more layers are overlapped with a light-transmitting coating resin and the light-receiving element is covered with a light-transmitting resin. It is intended to provide a photocoupler having a transmission efficiency.

That is, the present invention provides: (1) a facing type photocoupler in which a light emitting element and a light receiving element are opposed to each other, having a structure in which two or more light transmitting coating resins for protecting the light emitting element are stacked. (2) In a facing type photocoupler in which a light emitting element and a light receiving element are opposed to each other, a light transmitting polyimide is provided around the light receiving element.
A high transmission efficiency photocoupler (second invention), which has a structure covered with a resin-based resin , and (3) a facing type photocoupler in which a light emitting element and a light receiving element are opposed to each other to protect the light emitting element. Consisting of two or more light-transmissive coating resins, and
A high-transmission-efficiency photocoupler having a structure in which the light-receiving element is covered with a light-transmitting resin.
Invention)).

Hereinafter, the present invention will be described in detail. (About the First Invention) The first invention has a structure in which two or more light-transmitting coating resins for protecting the light-emitting element are laminated, and is replaced with the conventional "single-step coating of the light-transmitting protective agent". It has a structure in which a transmissive protective agent is applied in two or more steps (hereinafter, referred to as “two-step application of light transmissive protective agent”). Specifically, a structure having a spherical projection made of one or more light-transmitting resins (light-transmitting protective agent) on a light-transmitting protective agent for protecting a light-emitting element from thermal and mechanical stress. It is a photo coupler.

More specifically, in the first invention, the light-transmitting protective agent around the light emitting element is provided in two or more stages,
The radius of curvature of the second and subsequent light-transmitting protective agents is reduced, and the light-emitting element is improved so as to converge light more strongly, thereby improving the transmission efficiency of the photocoupler. . In the first invention, the light-transmitting core is used.
Although not limited, the silicone resin (light transmitting protective agent) is preferably a silicone resin.

(Second Invention) The second invention focuses on the periphery of the light receiving element, and has a structure in which the periphery of the light receiving element is covered with a light-transmitting polyimide resin . Specifically, the area around the light receiving element
This is a photocoupler having a structure in which the photocoupler is hemispherically covered with a polyimide resin, thereby improving the transmission efficiency of the photocoupler and improving the withstand voltage between input and output in the first invention.

That is, according to the first aspect of the present invention, in order for the light emitted from the light emitting element to be efficiently received by the light receiving element, the light transmitting protective agent (first silicone resin) having a large radius of curvature is provided on the light transmitting protective agent (first silicone resin). The protective agent (second silicone resin) having a small radius is mounted. The interface between the second silicone resin and the primary mold resin is electrically unstable and conductive, so that the distance between the input and output is reduced, and the distance between the input and output is different. In this case, the withstand voltage characteristic of the double-mold photocoupler having a longer length is deteriorated to some extent. The second aspect of the present invention also improves the withstand voltage characteristics.

In general, comparing the light emitting area of the light emitting element with the light receiving area of the light receiving element, the light receiving area of the light receiving element is larger. For this reason, light from the light emitting element is similar to light from a point light source, and requires a lens with a small radius of curvature to collect light. On the other hand, in the case of a light receiving element, since the light receiving area is large, even a lens having a larger radius of curvature than that of the light emitting element can collect light on a wide light receiving portion, thereby enabling efficient light reception.

Therefore, in the second invention, the distance between the input and the output can be made longer than that of the photocoupler having the "two-stage application of the light transmitting protective agent" structure of the first invention, and the same transmission efficiency with the same transmission efficiency can be obtained. In the case of the photocoupler of the light emitting element and the light receiving element, there is an advantage that the withstand voltage between the input and the output can be increased.
In addition, light-transmitting polyimide resin is used around the light receiving element.
It is characterized by having a covered structure.

(Regarding the Third Invention) The third invention is a photocoupler obtained by further improving the transmission efficiency and combining the first invention and the second invention. That is, the third invention is characterized in that the periphery of the light-emitting element is overlapped with two or more light-transmissive coating resins, and the periphery of the light-receiving element is further covered with the light-transmissive resin, thereby further improving the transmission efficiency. It is intended.

[0023]

Next, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2 show the first and second embodiments of the first invention, FIG. 4 shows the embodiment of the second invention, and FIG. 5 shows the embodiment of the third invention, respectively.

(Embodiment 1 of the First Invention) FIG. 1 is a sectional view of an opposing photocoupler according to an embodiment of the first invention. A light emitting side relay comprising a pair of two light emitting elements 11 and a light receiving element 12.
The pellets are mounted on the dove frame 15 and the light receiving side lead frame 16 by wire bonding. Also,
Similarly to the conventional photocoupler, the light emitting element 11 is coated with a silicone resin (first silicone resin) 17 which is a light transmitting protective agent for avoiding thermal and mechanical stress. In the first embodiment of the first invention, the silicon
This is a "two-step coating structure of a light-transmitting protective agent" in which an additional silicone resin spherical projection 17a as a second silicone resin is further coated on the resin resin 17.

The method of manufacturing the photocoupler according to the first embodiment will be described. First, the light emitting element 11 and the light receiving element 12 are pellet-mounted on the light emitting side lead frame 15 and the light receiving side lead frame 16. Wire-bond. Reference numeral 13 denotes a bonding wire (Au wire on the light emitting element side);
Is the same (Au line on the light receiving element side). Next, a silicon resin (first silicon resin) is applied to the light emitting element 11 and the bonding wire (the Au line on the light emitting element) 13 so as to cover them.
Resin) 17, air is blown at a constant pressure to form a flat portion at the top of the head, and is thermally cured. Further, a second silicone resin is dropped thereon to attach an additional silicone resin spherical projection 17a, which is heated and fixed again.

Thereafter, additional silicone resin spherical projections 17a are formed.
The light emitting side lead frame 15 and the light receiving side lead frame 16 having the above structure are combined so as to face each other, and molded with a primary mold resin (translucent resin) 18. The outside is molded with a secondary mold resin (light-shielding resin) 19 to manufacture a photocoupler.

The operation of the photocoupler will be described. The light emitting element 11 is turned on by an electric signal input from the input side lead of the light emitting side lead frame 15. This light passes through the silicone resin 17, the additional silicone resin spherical projections 17 a and the primary mold resin (translucent resin) 18, reaches the light receiving element 12, is again converted into an electric signal, and is converted into an electric signal. It is output from the output side lead of the lead frame 16.

(Concerning Condensing Power and Light Transmittance of Light Emitting Element) In the first embodiment, an additional silicone resin spherical projection having a small radius of curvature is provided on a silicone resin 17 having a large radius of curvature.
17a is formed so that the light from the light emitting element 11 is more strongly condensed, thereby improving the transmission efficiency of the photocoupler. Silicone resin 17
And the additional silicone resin spherical projection 17a has a wavelength of 700 to 1000.
The transmission for nm light is about 90% / mm, while
The transmittance of the primary mold resin (translucent resin) 18 is about 20%
/ Mm, additional silicon resin spherical projection
Providing 17a has an advantage that transmission loss can be reduced. Actually, when the length of the part A in FIG. 1 is about 400 μm and the length of the part B is about 300 μm, the transmission efficiency can be increased by about 10 to 20%.

(Regarding dielectric breakdown between input and output) In the first embodiment, the dielectric breakdown between input and output is generally caused by the additional silicone resin 17a and the primary mold resin (translucent resin) 18. It occurs at the portion B in FIG. 1 through the interface. The dielectric breakdown voltage of the silicone resin 17 and the additional silicone resin spherical projection 17a is 14 to 18 KV / mm, while that of the primary mold resin (translucent resin) 18 is 25 to 30 KV / mm. Therefore, the thickness of the additional silicone resin spherical projection 17a is set to 200 μm.
When it is set to about m, it will drop about 2-3 KV. However, since the total distance of the interface is small by attaching the additional silicone resin 17a as a sphere in the first embodiment, the reduction in the withstand voltage is reduced to about 1 KV (15 KV → 14 KV), and the withstand voltage level is reduced. Can be maintained.

(Embodiment 2 of the First Invention) FIG. 2 is a sectional view of an opposing photocoupler according to another embodiment of the first invention, which is applied when the area of the light receiving element 12 is large. This is an example. In other words, the second embodiment is an example in which the same silicone resin 17b and 17c are attached in addition to the additional silicone resin spherical projections 17a, and is the same as the first embodiment except for this point. When the area of the light receiving element 12 is large, it is effective to provide a plurality of additional silicone resin spherical protrusions 17a, 17b, and 17c,
Further, there is an effect that the ability can be increased with respect to the dielectric strength.

As shown in FIG. 3 (a diagram for explaining the dielectric breakdown between the light emitting element and the light receiving element), the dielectric breakdown in the portion B in FIG.
In the second embodiment, a plurality of additional silicone resin spherical projections are formed.
It is considered that the provision of 17a, 17b, and 17c reduces the probability of occurrence of discharge routes, and as a result, it is possible to increase the withstand voltage as compared with the first embodiment.

(Embodiment of the Second Invention) FIG. 4 is a sectional view of a photocoupler according to an embodiment of the second invention. This photocoupler has a light emitting element 21 made of a GaAs light emitting diode and a light receiving element 22 made of a Si phototransistor on a metal light emitting side lead frame 25 and a light receiving side lead frame 26, respectively. Glue. Next, the electrode on the side not bonded with the Au wire and the light emitting side lead frame 25 are bonded to each other by a bonding wire (light emitting element side Au wire) 23,
Electrode on the side not bonded with u-line and lead-free on the light-receiving side
24 to the bonding wire (Au wire on the light receiving element side) 24
To connect each.

Subsequently, a liquid silicone resin is dropped on the light emitting element 11 and formed into a hemispherical shape by surface tension.
The silicone resin 20 is formed by thermosetting. This is a "single-step coating structure" coated with a silicone resin 27, which is a light-transmitting protective agent, in order to avoid thermal and mechanical stress, like a conventional photocoupler. On the other hand, the light receiving element 22, is added dropwise a liquid polyimide resin thereon is molded in a hemispherical shape by surface tension, and thermosetting Porii
The mid resin 20 is formed.

A silicone resin 27 is provided on the light- emitting side , and a poly-silicon resin is provided on the light-receiving side.
After curing the imide resin 20, the light emitting element 21, the light receiving element 22
Light-emitting side lead frame 25 and light-receiving side lead
The dove frame 26 is joined, a primary mold resin (translucent resin) 28 is formed in the primary mold, and then a secondary mold resin (light-shielding resin) 29 is formed in the secondary mold. To complete the assembly. As a result, the light emitted from the light emitting element 21 is condensed lightly by the silicone resin 27, and
Cold resin proceeds (the translucent resin) in 28, light receiving element 22 side port
The light is condensed by the polyimide resin 20 and guided on the light receiving surface of the light receiving element 22.

[0035] This death Rico - down resin 27, a polyimide resin 20
, The coupling efficiency is about 1.5 times as high as that of the conventional photocoupler (see FIG. 6). In addition, it was confirmed that the withstand voltage between the input and the output withstands the voltage between the input and the output of 6 kV and the application time of 5 sec in all the devices.

(Embodiment 3) FIG. 5 is a cross-sectional view of a photocoupler according to an embodiment of the third invention. As shown in FIG. This is a photocoupler having a structure combining the embodiment of the second invention.
In this embodiment, the same material system as in the embodiment of the second invention is used.

The manufacturing method will be described. In this embodiment, only the light emitting element 31 side is different from the embodiment of the second invention. First, as in the first embodiment of the first invention, a silicon resin 37 is dropped on the light emitting element 31 and air is blown at a constant pressure to form a flat portion on the top of the head and heat cured. afterwards,
Further, a silicone resin 37a is dropped to obtain a "two-stage coating structure of a light-transmitting protective agent". On the other hand, the light-receiving element 32 has a liquid polyimide
Drop resin , mold into hemisphere with surface tension, heat cure
The polyimide resin 30 is formed.

Next, the silicone resin 37, 37a on the light emitting side ,
After the light-receiving side polyimide resin 30 is cured, the light-emitting side lead frame 35 and the light-receiving side lead frame are formed in such a manner that the light emitting element 31 and the light receiving element 32 face each other, as in the second embodiment of the present invention.
The primary mold is used to form a primary mold resin (light-transmitting resin) 38, and the secondary mold is used to form a secondary mold resin (light-shielding resin) 39. Complete.
In FIG. 5, reference numeral 33 denotes a bonding wire (the Au line on the light emitting element), and reference numeral 34 denotes the same (Au line on the light receiving element).

In the photocoupler of this embodiment, the light-collecting function of the hemispherical polyimide resin 30 on the light-receiving side is enhanced by the two-step application of the silicone resins 37 and 37a on the light-emitting side. At the same time, the value is up to about 1.7 times that of the conventional photocoupler (see FIG. 6). However, the input / output withstand voltage is slightly worse than that of the second embodiment so that about 70% of the devices withstand the same conditions as those of the second embodiment.

[0040]

The first invention has a structure in which two or more light-transmissive coating resins for protecting the light emitting element are stacked (a structure in which additional coating resin spherical projections are added).
This allows the input and output of the conventional double-mold photocoupler
Transmission efficiency of 10 while maintaining the strength of the insulation withstand voltage between outputs
The effect of improving by 20% occurs.

According to the second aspect of the present invention, a light-transmitting polyimide resin for condensing light is adhered to the periphery of the light receiving element of the double-mold photocoupler, so that the transmission efficiency is about 1.5 times that of the conventional photocoupler. This has the effect of having the same withstand voltage between input and output as that of the conventional photocoupler. Especially the second
The invention has the effect of improving the dielectric strength between input and output in the first invention. A third invention is a structure in which the first invention and the second invention are combined, that is, two or more light-transmitting coating resins are laminated around the light-emitting element, and further, a light-transmissive polyimide resin is laminated around the light-receiving element. , Which has the effect of further improving the transmission efficiency as compared with the first and second inventions.

[Brief description of the drawings]

FIG. 1 is a sectional view of a photocoupler according to an embodiment of the first invention.

FIG. 2 is a sectional view of a photocoupler according to another embodiment of the first invention.

FIG. 3 is a view for explaining dielectric strength breakdown between a light emitting element and a light receiving element of the photocoupler shown in FIG. 2;

FIG. 4 is a sectional view of a photocoupler according to an embodiment of the second invention.

FIG. 5 is a sectional view of a photocoupler according to an embodiment of the third invention.

FIG. 6 is a cross-sectional view of a conventional photocoupler.

[Explanation of symbols]

11, 21, 31, 41 Light emitting element 12, 22, 32, 42 Light receiving element 13, 23, 33, 43 Bonding wire (light emitting element side Au wire) 14, 24, 34, 44 Bonding wire (light receiving element side Au) line) 15, 25, 35, 45 light emitting side Li - Dofure - arm 16, 26, 36 and 46 receiving side Li - Dofure - arm 17, 2 7, 3 7,37a, 47 silicone - down resins 17a, 17b, 17c Additional silicone resin spherical projections 18, 28, 38, 48 Primary mold resin (light-transmitting resin) 19, 29, 39, 49 Secondary mold resin (light-shielding resin) 20, 30 Polyimide resin 50 filler −

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 31/12

Claims (4)

(57) [Claims] 1. A high-transmission type photocoupler in which a light-emitting element and a light-receiving element are opposed to each other, comprising a structure in which two or more light-transmitting coating resins for protecting the light-emitting element are stacked. Efficiency photo coupler. 2. A counter-type photocoupler is opposed to a light emitting element and a light receiving element, the periphery of the light receiving element Porii
A high transmission efficiency photocoupler characterized by having a structure covered with a mid resin . 3. An opposing photocoupler in which a light emitting element and a light receiving element are opposed to each other, wherein the optocoupler has a structure in which two or more light transmitting coating resins for protecting the light emitting element are stacked, and A high transmission efficiency photocoupler having a structure in which the periphery is covered with a light transmitting resin. 4. A light transmissive core for protecting a light emitting element.
The high transmission efficiency photocoupler according to claim 1 or 3, wherein the resin is a silicone resin.